黄土高原森林/非森林流域径流稳定性及其演变趋势对比

采用集中期、集中度等方法及M-K,Pettitt等非参检验法对比分析了黄土高原北洛河子午岭森林流域与相邻丘陵沟壑区非森林流域近50 a来的径流稳定性差异及演变趋势,为黄土高原地区生态治理的水文效应分析提供参考和借鉴.结果表明,黄土高原子午岭林区和非林区流域径流量年际尺度分布表现出一致的强变异性,年内分布均为双峰型特征,但林区峰型平缓,非林区陡峭.林区流域年内分布较非林区流域均匀,前者径流集中期较后者滞后1个月.近50 a来林区流域径流量无明显变化趋势,而非林区流域年、夏、秋及汛期径流量表现出显著性减少趋势,且有显著的跃变时间.无论径流过程或径流量年变化如何,林区稳定性要明显优于非林区流域.非林区流域的生态环境仍需要长时期的建设和维护.

Stationarity and Change Trend of Streamflows in Forest and Less Forested Watersheds on Loess Plateau

The stationarity of streamflows over the past 50years were investigated for well/poorly forested watersheds in the Beiluohe River basin on the Loess Plateau,using concentration degree and concentration period methods.The change trend and change point were checked with nonparametric M-K,Pettitt and Rank-sum tests.Results show that all the five watersheds studied were characterized by the high fluctuation of annual streamflow and the double peaks of inner-annual hydrograph.Forested ones presented mild slopes and less forested ones,steep shapes.In contrast,the streamflows were better distributed in well forested watersheds where the concentration period was 1month behind the poorly forested counterpart.Different components of the streamflow in forested watersheds did not show a significant trend or change point,while significant decrease and change points were detected in annual streamflow and the components in summer,fall and flood season for less forested watersheds in the past 50years.In both annual and inner-annual scales,the streamflow in forested watersheds was considered more stable than that of the less forested,which implies that less forested watersheds still demands a long-term construction and conservation for the eco-environment to recover.